Computer software application programs do not always require the high-capability computing hardware resources that are at their disposal. But if some critical code passage or whole application program must run at maximum efficiency, conventional systems dedicate the necessary computing hardware full time. In a few prior art multiprocessor systems that run applications that can be split and paralleled, pools of identical processor cores can be added in sufficient numbers to get the job done.
Some waste can be involved in the mismatching of software with modest resource requirements on high performance hardware platforms. When there is only one processor core available for all processing jobs, the waste of computing resources and power to operate them is unavoidable. High performance hardware is usually associated with large demands on operating power input. If such high performance is going to waste much of the time, the marginal operating power needed over more modest equipment is pure cost with no benefit.
Since their introduction in the 1970's, microprocessors and microcomputer systems have been providing ever more increasing levels of performance, reliability, and capability. Every few years since then has seen the microprocessor evolve to new, higher levels. Clock speeds got higher, memory subsystems, cache memories, and peripherals were brought in on-chip as semiconductor technology advances permitted. Complex instruction set computers (CISC) and reduced instruction set computers (RISC) evolved, and instruction and data bus widths reached 32-bits, 64-bits, and even 128-bits.
Device technologies have been changing. The first Intel microprocessors, e.g., the 4004, used p-channel metal oxide semiconductor (PMOS) technology. Later processors used n-channel metal oxide semiconductor (NMOS) technology. An RCA microprocessor family, the 1802, used low-power complementary metal oxide semiconductor (CMOS) technology. Some very high performance microprocessors in the 1970's and later used bipolar transistor technology. Today's MOS technology used in microprocessors has high leakage currents that require the operating power to actually be interrupted, or switched off, in order to reduce power consumption completely in inactive circuits.
In general, higher clock speeds and denser functionality has meant increased power consumption and hence dissipation. Such power dissipation causes undesirable heating and, in battery-operated portable systems, leads to reduced battery life. Constantly using a processor that uses a lot of power and that exceeds the needs of the application software can lead to significant power waste and costs.